Super design! Test your LEDs at 10 mA (or what ever you are going to run them at). You will probably find they run at a lower voltage at less current.Here you go. This is a layout using 5 mm LEDs on .5" spacing. The strips are somewhat offset from the blue field and of course the black dots represent white LEDs. The overall size is 15.5" x 9.65". You could reduce the overall size by using 3 mm LEDs on .4 mm spacing. You might get a better effect by putting the LEDs behind a plastic diffuser.View attachment 109971
You will need a total of 758 LEDs; 327 Red, 338 White, and 93 Blue.
758 x 10 mA = 7.58 amps
You will need a power supply capable of delivering at least that much current. Unfortunately, you're going to find that they ain't cheap!